Abrasive articles having mechanical fasteners

ABSTRACT

Fixed abrasive articles comprising a substrate having an abrasive surface and an attachment surface, and at least one engaging projection are described. Generally, the engaging projection comprises a top surface having a top surface edge and an attachment end attached to the attachment surface of the substrate. The area of attachment between the attachment end and the attachment surface is bounded by an attachment perimeter. The engaging projection also comprises a mantle surface extending from the top surface edge to the attachment perimeter. At least one profile of the mantle surface is substantially convex from a point of maximum width along the profile to the attachment perimeter.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/825,220, filed Sep. 11, 2006, the disclosure of whichis incorporated by reference herein in its entirety.

FIELD

The present disclosure relates to fixed abrasive articles having amolded mechanical fastener.

BACKGROUND

It is common to use certain hook-and-loop type mechanical fasteners forconnecting fixed abrasive articles to abrading tools. One approach usesthin, molded male fasteners (e.g., “hooks”) with low loft loopmaterials, most commonly textile “loop” materials as the femalecomponents. For these uses generally low cost and appropriate attachmentstrength are important. The word “loop”, as used in this document, alsoincludes low lying, free sections of fabric filaments, such as those ofa textile fabric, capable of mechanically engaging with a male fastenercomponent, this use of the word being in accordance with its currentgeneral use in the art of separable fasteners.

Engaging projections have been directly molded as disclosed for examplein U.S. Pat. No. 5,315,740, which describes a re-entrant hook, i.e., ahook having a tip-portion that curves over and down toward the basesheet from the upper end of the hook to define a fiber-retaining recesson the underside of the hook. It is also known to cap molded stems onwebs. Mushroom-shaped engaging projections obtained by this process aredisclosed in, e.g., U.S. Pat. Nos. 5,679,302; 5,879,604; 6,287,665; and6,627,133. U.S. Pat. No. 6,470,540 uses a hot extruded layer fordeforming stems, which results in semi-spherical mushroom heads. In U.S.Pat. No. 3,550,837, a male fastener member is described wherein eachengaging projection is constituted by an irregularly shaped granule witha special multifaceted surface, adhesively adhered to the base. In U.S.Pat. No. 3,922,455, nibs of various shapes are grafted onto linearfilaments, the linear filaments, protruding from a base, forming theengaging elements of a male fastener component. In PCT publication WO01/33989, particles are, with a scatter head of a scatter coater,randomly scattered, and fixed onto a base. Each engaging projection isconstituted by several agglomerated particles, though some individualparticles may also be left present.

There is a continuing need to provide low-cost male mechanical fastenerswith advantageous properties.

SUMMARY

In one aspect, the present disclosure provides a fixed abrasive articlecomprising a substrate having an abrasive surface and an attachmentsurface, and at least one engaging projection. The engaging projectioncomprises a top surface having a top surface edge and an attachment endattached to the attachment surface of the substrate. The area ofattachment between the attachment end and the attachment surface isbounded by an attachment perimeter. The engaging projection alsocomprises a mantle surface extending from the top surface edge to theattachment perimeter. At least one profile of the mantle surface issubstantially convex from a point of maximum width along the profile tothe attachment perimeter.

In some embodiments, the engaging projection is directly attached to theattachment surface of the substrate. In some embodiments, the engagingprojection is indirectly attached to the attachment surface of thesubstrate. In some embodiments, at least one intermediate layer isinterposed between the attachment end of the engaging projection and theattachment surface, optionally wherein the intermediate layer isselected from the group consisting of an adhesive, a primer, a binder, aresin, a polymeric film, and combinations thereof.

In another aspect, the present disclosure provides a fixed abrasivearticle comprising a first substrate having an abrasive surface and anattachment surface, and an attachment layer. The attachment layercomprises a second substrate having a first surface and a secondsurface, wherein the first surface of the second substrate is attachedto the attachment surface of the first substrate. The attachment layerfurther comprises an engaging projection comprising a top surface havinga top surface edge, and an attachment end attached to the second surfaceof the second substrate. The area of attachment between the attachmentend and the second surface is bounded by an attachment perimeter. Theengaging projection also comprises a mantle surface extending from thetop surface edge to the attachment perimeter. At least one profile ofthe mantle surface is substantially convex from a point of maximum widthalong the profile to the attachment perimeter. In some embodiments, thefirst surface of the second substrate is attached to the attachmentsurface of the first substrate via an adhesive layer, optionally whereinthe adhesive layer comprises an adhesive selected from the groupconsisting of a pressure sensitive adhesive, a heat-activated adhesive,radiation curable adhesive, and moisture curable adhesive.

In some embodiments, the fixed abrasive articles of the presentdisclosure further comprise an abrasive layer at the abrasive surface ofthe substrate. In some embodiments, the abrasive layer is directlyattached to the abrasive surface of the substrate. In some embodiments,the abrasive layer is integral with the abrasive surface of thesubstrate. In some embodiments, the abrasive layer is indirectlyattached to the abrasive surface of the substrate.

In some embodiments, the abrasive layer comprises a make coat, abrasiveparticles at least partially embedded in the make coat, and, optionally,a size coat over the abrasive particles. In some embodiments, theabrasive layer comprises a primer and abrasive particles attached to theprimer. In some embodiments, the abrasive layer comprises abrasiveparticles dispersed in a binder, optionally wherein the binder isselected from the group consisting of inorganic binders, organicbinders, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary abrasive article according to someembodiments of the present disclosure.

FIG. 2 illustrates an exemplary engaging element according to someembodiments of the present disclosure.

FIG. 3 illustrates a cross-section of the exemplary engaging element ofclaim 2.

FIGS. 4 a-4 c illustrate the cross sections of concave engagingelements.

DETAILED DESCRIPTION

In one aspect, the present disclosure provides a fixed abrasive articlecomprising a substrate having an abrasive surface and an attachmentsurface. The attachment surface includes attached engaging projections,which may be used to connect the fixed abrasive article to an abradingapparatus.

Fixed abrasive articles are often used with dual action sanders (“DAsanders”) which are well known in the art. Such sanders with back-uppads may be used for light duty sanding operations such as light sandingof painted surfaces between paint coats and sanding with very finesandpaper to remove small paint imperfections such as dust nibs from thefinal paint coat. This type of sanding imparts little stress to theattachment interface. Such back-up pads may also be used for medium dutysanding operations such as final preparation of a workpiece surface forprimer painting and sanding a workpiece surface having a primer paintthereon in preparation for subsequent painting. Light to medium downwardpressures are typically applied during these types of sandingapplications and impart a moderate amount of stress on the attachmentinterface. However, such sanders and back-up pads are often used underheavy duty sanding operations such as paint stripping or removing excessbody filler where fairly heavy downward pressure would be applied by theoperator. The back-up pad is often inclined at a relatively steep anglewith respect to the workpiece surface and may also be pushed intocrevices and over fairly sharp contours. The paint or body filler on theworkpiece surface provides substantial resistance to the abrasivesurface of the abrasive article attached to the back-up pad so that aconsiderable sanding force is often required to remove the paint or bodyfiller. Such aggressive, heavy sanding operations apply substantialstress on the hook and loop attachment interface.

In general, the means (e.g., mechanical attachment systems) used toattach a fixed abrasive article to, e.g., a back-up pad may be requiredto withstand both shear forces and peel forces. In addition, in someembodiments, the peel force may be selected to be high enough towithstand the forces encountered during use, but low enough to provideease of removal and/or repositioning.

Generally, any known form of fixed abrasive article may be used.Exemplary fixed abrasive articles forms include discs, sheets, strips,circles, ovals, polygons, and “daisy-shapes.”

A representative fixed abrasive article 10 is shown in FIG. 1. Abrasivearticle 10 includes substrate 20 having abrasive surface 21 andattachment surface 22. Engaging projections 30 are attached toattachment surface 22.

Generally, any known substrate may be used, e.g., paper, polymericfilms, vulcanized fiber, woven and nonwoven webs, fabrics (e.g., knittedfabrics), cloths, scrims, meshes, foams, foils, treated versionsthereof, and combinations thereof. Exemplary polymeric films includeextruded, blown, or cast films of polyamide, polyester, or polyolefin.Exemplary woven fabrics include plain or twill weaves of polyamide,polyester, rayon, or cotton yarns. Exemplary nonwoven fabrics includeair laid, calendared, carded, or melt-blown fabrics of natural orsynthetic fibers. Nonwoven fabrics may be crosslapped.

In some embodiments, is the substrate may comprise paper, including,e.g., treated, primed, or otherwise modified papers. Any of a variety ofpapers customarily employed as coated abrasive backings may be employedto provide the paper sheet. In some embodiments, the paper sheet is acylinder paper. In some embodiments, the paper has a basis weight in therange of about 100 to 400 grams per square meter (gsm). In someembodiments, the paper has tensile strength at break of at least about40 kilograms per 25 millimeters (kg/25 mm) in the machine direction, andat least about 16 kg/25 mm in the cross machine direction. An exemplarycylinder paper having a basis weight of 220 gsm is commerciallyavailable from FiberMark located in Battleboro, Vt.

In some embodiments, the substrate is foraminous, including, e.g.,scrims, screens, or meshes, including treated or modified versionsthereof. The foraminous substrate may be made of natural or syntheticfibers. Such substrates may be knitted or woven in a network havingintermittent openings spaced along the surface of the substrate. Thesubstrate need not be woven in a uniform pattern but may also include anonwoven random pattern. Thus, the openings may either be in a patternor randomly spaced. The foraminous substrate openings may be of anydesired shape including, e.g., polygonal shaped (e.g. rectangular,diamond, triangular, or octagonal shaped) or a combination of suchshapes.

In some embodiments, the foraminous substrate, e.g., a scrim, comprisesa first set of rows of separated fibers deployed in a first directionand a second set of fibers deployed in a second direction to provide agrid including multiple adjacent openings. The substrate may alsocomprise an open mesh including, e.g., those selected from the groupconsisting of woven or knitted fiber mesh, synthetic fiber mesh, naturalfiber mesh, metal fiber mesh, molded thermoplastic polymer mesh, moldedthermoset polymer mesh, perforated sheet materials, slit and optionallystretched sheet materials and combinations thereof.

In some embodiments, the substrate may comprise multiple layers of thesame or different materials. In some embodiments, the substratecomprises two or more polymeric films. In some embodiments, one layer(e.g., a paper, fabric, cloth, scrim or high melting point polymericfilm (e.g., polyester)) may be selected to provide, e.g., the desiredmechanical properties of the fixed abrasive article. In someembodiments, one layer (e.g., a low melting point polymeric film (e.g.,polyethylene or polypropylene)) may be selected to provide, e.g., asurface suitable for attachment to the engaging elements. In someembodiments, at least one layer comprises a foam (e.g., an open cellfoam or a closed-cell foam).

Referring to FIG. 1, abrasive layer 25 is attached to abrasive surface21. In some embodiments, abrasive layer 25 is directly attached toabrasive surface 21. In some embodiments, one or more layers (e.g.,primer layers, tie layers, adhesive layers) may be interposed betweenabrasive layer 25 and abrasive surface 21. In some embodiments, theabrasive layer is integral with the abrasive surface of the substrate

Generally, any known abrasive layer may used. In some embodiments, theabrasive layer comprises a plurality of abrasive particles at leastpartially embedded in a make coat. In some embodiments, a size coat isprovided over the abrasive particles. In some embodiments, the abrasivelayer comprises a primer and abrasive particles attached to the primer.

In some embodiments, the abrasive layer comprises shaped abrasivestructures. In some embodiments, the shaped abrasive structures comprisea cured resin binder and abrasive particles. In some embodiments, theshaped abrasive structures are porous, e.g., in some embodiments, theshaped abrasive structures comprise interconnected pores. In someembodiments, the cured resin binder is formed by curing a particulate,room temperature solid, softenable, curable binder material. In someembodiments, the particulate curable binder material comprises organiccurable polymer particles. The particulate curable polymers are capableof softening on heating to provide a curable liquid capable of flowingsufficiently so as to be able to wet either an abrasive particle surfaceor the surface of an adjacent curable binder particle.

In some embodiments, the abrasive layer may comprise a plurality ofabrasive particles dispersed in an organic or inorganic binder. Organicand inorganic binders suitable for producing abrasive layers are knownin the art.

In some embodiments, the outer surface of the abrasive layer issubstantially parallel to the abrasive surface of the substrate. In someembodiments, the abrasive layer is textured, e.g., the abrasive layermay be embossed to provide an ordered and/or random pattern of raisedand lowered regions. Methods of providing a textured surface are knownand described in, e.g., U.S. Pat. No. 5,152,917 (Pieper et al.).

In some embodiments, an abrasive article of this invention contains anabrasive coating with at least one abrasive composite layer thatincludes a plurality of shaped, preferably precisely shaped, abrasivecomposite structures. The term “shaped” in combination with the term“abrasive composite structure” refers to both precisely shaped andirregularly shaped abrasive composite structures. An abrasive article ofthis invention may contain a plurality of such shaped abrasive compositestructures in a predetermined array on a backing. Alternatively, theshaped abrasive composites may be in a random shape or an irregularplacement on the backings.

Any known abrasive particles may be used. The average particle size ofthe abrasive particles can range from about 1 to 1800 micrometers (39 to71,000 microinches), typically between 2 and 750 micrometers (79 to30,000 microinches), and most generally between 5 and 550 micrometers(200 to 22,000 microinches). The size of the abrasive particle istypically specified to be the longest dimension of the abrasiveparticle. In most cases there will be a range distribution of particlesizes. In some instances, the particle size distribution is tightlycontrolled such that the resulting abrasive article provides aconsistent surface finish on the workpiece being abraded.

Exemplary abrasive particles include fused aluminum oxide, ceramicaluminum oxide, sol gel alumina-based ceramics, silicon carbide, glass,ceria, glass ceramics, fused alumina-zirconia, natural crushed aluminumoxide, heat treated aluminum oxide, zirconia, garnet, emery, cubic boronnitride, diamond, particulate polymeric materials, metals andcombinations and agglomerates thereof.

Examples of conventional hard abrasive particles include fused aluminumoxide, heat treated aluminum oxide, white fused aluminum oxide, blacksilicon carbide, green silicon carbide, titanium diboride, boroncarbide, tungsten carbide, titanium carbide, diamond (both natural andsynthetic), silica, iron oxide, chromia, ceria, zirconia, titania,silicates, tin oxide, cubic boron nitride, garnet, fused aluminazirconia, sol gel abrasive particles and the like. Examples of sol gelabrasive particles can be found in U.S. Pat. No. 4,314,827 (Leitheiseret al.); U.S. Pat. No. 4,623,364 (Cottringer et al); U.S. Pat. No.4,744,802 (Schwabel); U.S. Pat. No. 4,770,671 (Monroe et al.) and U.S.Pat. No. 4,881,951 (Wood et al.).

The term abrasive particle, as used herein, also encompasses abrasiveagglomerates, e.g., single abrasive particles bonded together with apolymer or ceramic to form an abrasive agglomerate. Abrasiveagglomerates are further described in U.S. Pat. No. 4,311,489(Kressner); U.S. Pat. No. 4,652,275 (Bloecher et al.); U.S. Pat. No.4,799,939 (Bloecher et al.), and U.S. Pat. No. 5,500,273 (Holmes etal.). Alternatively, the abrasive particles may be bonded together byinter-particle attractive forces.

The abrasive particle may also have a shape associated with it. Examplesof such shapes include rods, triangles, pyramids, cones, solid spheres,hollow spheres and the like. Alternatively, the abrasive particle may berandomly shaped.

Abrasive particles can be coated with materials to provide the particleswith desired characteristics. For example, materials applied to thesurface of an abrasive particle have been shown to improve the adhesionbetween the abrasive particle and the polymer. Additionally, a materialapplied to the surface of an abrasive particle may improve the adhesionof the abrasive particles in the softened particulate curable bindermaterial. Alternatively, surface coatings can alter and improve thecutting characteristics of the resulting abrasive particle. Such surfacecoatings are described, for example, in U.S. Pat. No. 5,011,508 (Wald etal.); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S. Pat. No. 5,009,675(Kunz et al.); U.S. Pat. No. 4,997,461 (Markhoff-Matheny et al.); U.S.Pat. No. 5,213,591 (Celikkaya et al.); U.S. Pat. No. 5,085,671 (Martinet al.) and U.S. Pat. No. 5,042,991 (Kunz et al.).

Referring to FIGS. 2 and 3, engaging projection 30 comprises attachmentend 33 attached to attachment surface 22. In some embodiments,attachment end 33 is directly attached to attachment surface 22. In someembodiments, the attachment end of a projection may be indirectlyattached to the attachment surface (i.e., one or more intervening layers(e.g., primer layers, tie layers, adhesive layers, polymeric films)) maybe interposed between the attachment end of a projection and theattachment surface of the substrate. Exemplary polymeric films include,e.g., low melting point polymeric films including, e.g., polyethyleneand polypropylene.

Attachment perimeter 35 indicates the location where engaging projection30 first contacts attachment surface 22, wherein the area of attachmentbetween the engaging projection and the attachment surface of thesubstrate is bounded by this attachment perimeter. Edge 32 indicates theperimeter of top surface 31 of engaging projection 30. Mantle surface 34is the surface of engaging projection 30 extending from edge 32 toattachment perimeter 35.

Referring to FIG. 3, a cross-section of engaging projection 30 takenalong line 3-3 of FIG. 2 is shown. Mantle profile 44 intersects topsurface 31 at intersection point 42. Edge angle 46 is defined by theinterior angle between line 45, which is tangent to mantle profile 44,and line 47, which is parallel to top surface 31. In some embodiments,the edge angle is substantially constant. In some embodiments, the edgeangle varies around the perimeter of the top surface of the engagingprojection. In some embodiments, the edge angle is at least about 15degrees (15°). In some embodiments, the edge angle is at least about20°, at least about 30°, or even at least about 40°. In someembodiments, the edge angle is no greater than about 85°. In someembodiments, the edge angle is no greater than about 80°, or even nogreater than about 70°.

Engaging projection 30 is a substantially convex engaging projection. Asused herein, an engaging projection is “substantially convex” if itsmantle profile is substantially convex. As used herein, a mantle profileis “substantially convex” if at least about 75% of the portion of themantle profile extending from the point of maximum width 43 toattachment perimeter 35 is convex relative to reference line 40.Reference line 40 is perpendicular to attachment surface 22 and passesthrough center point 41 of the region of contact between engagingprojection 30 and attachment surface 22. The point of maximum width isthe location on the mantle profile that is furthest from reference line40. In some embodiments, the point of maximum width corresponds to thelocation of the edge, i.e., the intersection between the top surface andthe mantle surface of the engaging projection.

In some embodiments, at least about 80%, in some embodiments, at leastabout 85%, in some embodiments, at least about 90%, 95%, or evensubstantially 100% of the mantle profile extending from the point ofmaximum width to the attachment perimeter is convex relative to thereference line.

Cross sections of exemplary, substantially concave engaging projectionsof the prior art are shown in FIGS. 4 a-4 c. In each case, the portionof mantle profiles 44 a, 44 b, and 44 c extending from point of maximumwidth 43 a, 43 b, and 43 c to attachment perimeters 35 a, 35 b, and 35 care concave relative to reference lines 40 a, 40 b, and 40 c,respectively.

The edge angle between the top of the deformed projection and the mantlesurface may vary over a broad range. In some embodiments, an edge anglethat is too small may weaken the fastener, e.g., by weakening theoverhanging rim by making it too thin, subject to bending or breaking.Therefore, in some embodiments the contact angles are between, 20degrees (20°) and 85° and, in some embodiments, between 30° and 80°. Askilled person can achieve this by suitably selecting the conditions inthe method, such as the materials of the particles and the contactsurface, the contact period time and other details of the contactdeformation step.

In some embodiments, at least some engaging projections are providedwith a mantle profile that strictly tapers from the top surface edge tothe attachment perimeter. Strictly tapering means that the nearer theengaging projection gets to the substrate, the narrower the projectionbecomes. For example, engaging projection 30 of FIGS. 2 and 3 isstrictly tapering.

Generally, in some embodiments, an engaging projection that is strictlytapering will pull engaged fibers down to the attachment surface of thesubstrate when a shear load is applied to the fastener without thefibers being caught at a non-tapered portion displaced from theattachment surface of the base. In some embodiments, the torque on theengaging projection is minimized so the substrate can be weaker, and, insome embodiments, can be cheaper, more flexible, and/or thinner.Furthermore, the attachment side of the fixed abrasive article may havea relatively large surface area formed by the plurality of engagingprojection top surfaces, making this surface smooth to the touch, whilealso having a relatively low total surface area of the projectionattached ends connected to the substrate, thereby increasing theflexibility of the abrasive article.

In addition to the edge angle, engaging projection 30 may becharacterized by the ratio of the perimeter of top surface 31 to theheight. In some embodiments the ratio of top surface perimeter to heightis about 1.1 to about 50. In some embodiments, this ratio is at leastabout 1.2, about 1.5, or even at least about 2. In some embodiments,this ratio is no greater than about 40, no greater than about 30, oreven no greater than about 25. Engaging projection 30 may also becharacterized by the ratio between the perimeter of top surface 31 toattachment perimeter 35.

A variety of methods may be used to form a fixed abrasive article havingone or more substantially convex engaging elements attached to itsattachment surface. In some embodiments, the substantially convexengaging elements may be formed directly on the attachment surface ofthe substrate of the fixed abrasive article.

For example, in some embodiments, the substantially convex engagingelements may be formed from particles of a material, e.g., athermoplastic material may be affixed to the attachment surface of thesubstrate, forming a multiplicity of thermoplastic projections extendingfrom the attachment surface to corresponding terminal ends. The word“particle”, as used herein, refers to a solid, liquid or semi-liquidparticle, including, for example, granules, pellets, powders anddroplets. In some embodiments, the particles may be uniformly affixed tothe substrate. In some embodiments, the particles may be randomlyaffixed to the substrate. In some embodiments, at least the terminalends of the formed projections are constituted by the particles thatwere affixed to the attachment surface.

In a subsequent step, the terminal ends of the projections are contactedwith the contact deformation surface of a deforming means underconditions (e.g., temperature, pressure and time) sufficient to achievethe desired deformation and, thus, the desired engaging projections.During the contact, the terminal ends of the projections are heatedabove a softening temperature while the attachment surface is generallykept cold enough to provide for suitable stability of both the substrateattachment surface and the portions of the engaging projections adjacentto the substrate attachment surface. The contacted surface is thencooled forming the top surface of the engaging projection.

Generally, deforming means are well known and include, but are notrestricted to, hot rolls, plates, and elongated nips (e.g., variablenips). The heating of the terminal ends of the particles can be providedby, e.g., a pre-heater or the contact surface of the deforming means, orboth. Exemplary preheating means include heated platens, radiant heatsources, and hot fluids (e.g., hot gases).

The skilled person will be able to select a way of keeping the base and,also, the attached ends of the projections cold enough, thereby solidenough, to prevent undesired deformation thereof. One exemplary way toachieve this includes keeping the back of the base in contact with acooled surface.

In some embodiments, the top surface of the deformed particles, i.e. theprojections, can be formed by a contact deformation surface that can besmooth. In some embodiments, the contact surface may be textured orroughened, e.g., sandpaper-like or grooved. However, in someembodiments, the contact deformation surface will be essentially flat,even if it is not planar in the true geometrical sense. In someembodiments, post treatments of the projections could be used to makethe top surface not essentially flat, such as using non-contact heattreatment.

During the contacting of the heated terminal end with the contactdeformation surface, a contact area is created bordered by a contactline. Along at least a part of the contact line the heated terminal endis provided with an acute contact angle.

The contact angle is influenced by the surface energies (i.e. surfacetension) of the contact surface and of the heated terminal end of thematerial, as well as the temperature and time of contact. The formed topsurface is thus bordered, at least partly, by an edge having an angleinfluenced by the acute contact angle. The contact angle will beaffected by the surface energy of the particles, the surface energy ofthe contact surface, and their relative interfacial energy.

If there is essentially no molecular orientation of the particles orformed projections, the contact angle is mainly determined by thesurface energies of the particle polymers and the contacting surface.The contact angle is furthermore influenced by the contact time, whichshould be selected appropriately. Subsequent cooling of the projectionspreserves the edge angles of the projections and can be selected, forexample, from ambient cooling, contact cooling, cooling with fluids(e.g., gases such as air).

The substrate can be any suitable continuous or discontinuous base websuch as a porous or nonporous polymer film, a laminate film, a nonwovenweb, a paper web, metal films, foils or the like. The substrate could bemodified by any known method such as by being printed, embossed, flametreated, laminated, particle coated, colored, or the like.

A polymer film used as a substrate can be oriented or unoriented. Insome embodiments, essentially unoriented films may be desirable. Theattachment surface of the substrate can be smooth or rough. For example,in some embodiments, the attachment surface can be roughened withparticles previously scattered and affixed thereon.

The particles should be brought and fixed on the substrate in a way thatat least the terminal ends of the projections can be formed from theparticles. Projections can consist completely of the particles withoutany further modification of said particles. For bringing and affixingthe particles to the (smooth or roughened) attachment surface, severalmethods are taught, e.g., random scattering and adhering, for example,in PCT publication WO 01133989, the entire disclosure of which is herebyincorporated by reference.

The material forming the substrate can be independently selected fromthe material forming the particles. In some embodiments, differentparticles of different materials, shapes and/or sizes, may be used.Also, mixtures of particles of different properties could be used. Thedensity of the projections can be varied during the process. Also, bychoosing a thin substrate, e.g. a suitable film, a thin fastener canreadily be made, the thickness can be further decreased by using smallparticles resulting in small projections which, in some embodiments, mayalso function especially well with thin loop fabrics. The symmetry ofthe method and the deformed projections also can provide an isotropicfastener.

In some embodiments, it may be desirable to extend the contact timebetween the deforming surface and the particles, e.g., so that there ismore time for the surface tension effects to create acute contact anglesso that the engaging projections have more acute edge angles. In someembodiments, the process can be run at a lower speed. In someembodiments, an elongated variable nip that gradually compressivelydeforms the terminal ends of the particles or projections can be used.

The deformed projections can be solidified, e.g., by cooling, in theirmost compressed state. It is also possible that after the deformedprojections are in their most compressed state and before the deformedprojections are in their final solidified state, the deformedprojections are somewhat lengthened by stretching them as they areremoved from the deforming surface. For example, in some embodiments,the terminal ends of the deformed projections can be stretched from thesubstrate by opening a nip while they are still attached to thedeforming surface, thereby causing the projections to get slimmer intheir middle section.

In some embodiments, e.g., when many small projections are desired, itmay be useful to form at least some deformed projections comprising oneparticle per deformed projection. This may make the process lessexpensive than forming the projections from multiple small particles, asless expensive larger particles can be used to form the projections. Insome embodiments, this can be inexpensively achieved by uniformlyscattering suitable polymer powder particles over a moving substrate ata suitable distance to provide the projections or particles.

In some embodiments, molecularly unoriented thermoplastic polymers arepreferred for attaching the particle to the substrate in the firstmethod. Therefore, in some embodiments of the first method, the providedthermoplastic particles are unoriented particles, which can be one ormore types of particles selected from a group including: (a) granules ofa powder made with size reduction from pellets; (b) granules from areactor powder; (c) granules from a precipitated powder; and (d)droplets.

Reactor powder means polymer powder taken from a polymer manufacturingreactor, before palletizing. Granules from a reactor or precipitatedpowder, as used herein, also include granules, of such powder, furthersize-reduced. Droplets may be solid or not, when provided, brought andaffixed to the front surface. Softening of the particle as they areattached to the substrate can further decrease any residual orientationin the particles.

In the first method, the affixing of the particles to the front surfaceof the substrate includes keeping the particles, brought to the frontsurface, at least partly, at a temperature above their softeningtemperature.

In some embodiments, the engaging projections may be formed on a carrierand subsequently transferred to the attachment surface of the fixedabrasive article. For example, in some embodiments, particles (e.g.,polymer particles) may be dispersed on the surface of the carrier.Generally, the surface may be pretreated to provide a suitable surfaceenergy and desirable release characteristics relative to the particles.In some embodiments, particles may be provided in at least a semi-liquidstate or softened state of suitable viscosity. In some embodiments, theparticles can be brought into this state after their deposition on thesurface of the carrier by, e.g., heating. The resulting softened orsemi-liquid particles are referred to as preform projections, where a“preform projection” is defined as a projection that, to at least someextent, has been preformed into the shape of the final engagingprojection at the ultimate top surface end, which is in contact with thesurface of the carrier, and extending to the terminal ends of thepreform projection, which will ultimately provide the attachment end.

The preform projections along their edges contacting the carrier willform contact angles, which will be influenced by the surface energies ofthe polymer particles and the carrier surface. The polymer particles aremaintained in a softened or semi-liquid state for a suitable period oftime so that they may form an acute contact angle at least along aportion of their edges contacting the carrier.

The preform projections can then be at least partially solidified andbrought into contact with the attachment surface of the fixed abrasivearticle, thereby affixing the terminal ends of the preform projectionsto the attachment surface, while essentially maintaining the shape ofthe edge formed by contact with the carrier. The preform projections canthen be further solidified to a sufficient degree so that the preformprojections can be released from the carrier and transferred to theattachment surface, thereby forming engaging projections attached to thefixed abrasive article. These formed engaging projections project fromattachment end (now attached to the attachment surface of thesubstrate), to the top surface, which was formed on the carrier. Theflattened tops at least partially overhang the substrate forming a rim,and are bordered, at least partly, by an edge having an angle which isinfluenced by the acute contact angle, as described above.

Suitable particles capable of being in a liquid or semiliquid (i.e.,softened or suitably pliable) state; and capable of becoming solid areknown. The particles can be, for example, droplets of liquid suspensionsetc., solidifiable by irradiation, or they can be thermoplasticparticles, as described above. The carrier can be any suitable carrier,e.g., a sheet-form substrate, e.g., a film, as described above.

The skilled person, familiar with the field of surface energy, surfacetension and wetting, can select a combination of a suitable polymer forthe particles and a carrier or the appropriate surface treatment for thecarrier. The skilled person can also select particles having a suitableviscosity at the temperature of the carrier such that the particles willwet the carrier within a suitable time. The surface energy of thecarrier may be formed by known materials and methods, such assiliconized surfaces, fluorochemicals, corona discharge, flame or thelike.

Generally, the carrier surface should be able to release the particularpolymer particles used, whether semi-liquefied or solidified. It isknown that certain release surfaces can release certain polymers but areunable to release other polymers. For example, a polyethylene releasesurface can release suitable polypropylene particles but may not releasecertain polyethylene particles as they tend to weld or fuse to eachother. The word “release” as used herein refers to the phenomenon wherethe particles are detached from the contact release surface withoutunacceptable damage or loss of material of the particles or preformprojections.

The carrier surface can be smooth or suitably structured or roughened,e.g., grooved, as known from the art. Dispersing of the particles ontothe release surface can be performed in any suitable way, for example,by scattering the particles with a scatter unit. In some embodiments,the particles are dispersed at a rate per unit surface area so that theyform preform projections where one particle can form one preformprojection. The particles may be distributed uniformly or randomly. Theparticles may also be dispersed according to a predefined pattern.

The particles can be brought into the at least semi-liquid state before,during and/or after dispersing of the particles onto the contact releasesurface. “At least semi-liquid” means liquid or semi-liquid. A suitableway of liquefying will depend on the properties of the selected polymer,and can include, for example, heating, thinning, solving, emulsifying,dispersing, etc.

A solidity (degree or extent of solidification) suitable for contactingand affixing the preform projections from the carrier to the attachmentsurface of the fixed abrasive article substrate can be decided by theskilled person, depending on the particular circumstances. It willusually, but not necessarily, require a more solid state than the one inwhich the preform projections have been formed on the carrier. In someembodiments, the preform projections should be solid enough to keep, atleast partly, their shape while being contacted with the attachmentsurface. In some embodiments, the solidity is selected to maintain atleast a minimum free height and also a suitable edge angle of thepreform projections. Setting the necessary solidity in the preformprojections will be material-dependent, and can include cooling, drying,heating, crosslinking, curing, chemical treatment, etc.

The preform projections of suitable solidity, sitting on the carrier,can be covered by the attachment surface such that the attachmentsurface contacts and fixes with the preform projection terminal ends.The terminal ends are the ends farthest from the carrier surface. Beforecontacting with the attachment surface, the preform projections can beprovided or supplemented with further added dispersed particles or thelike, which will attach to the preform projections. It is possible thatthe attachment surface is contacted with the preform projections whenthe preform projections are in a semiliquid state. In this case it ispossible that, after the contacting and before a final solidification,the preform projections are somewhat lengthened by stretching while thepreform projections are removed from the carrier thereby causing thepreform projections to get slimmer in their middles.

The affixing of the attachment ends of the preform projections to theattachment surface can be obtained by, e.g., adhering with an addedadhesive, resin, binder, solution, etc., and/or by crosslinking withultraviolet irradiation. In some embodiments, affixing can beaccomplished using the inherent adhesion of the contacted materials(i.e., attachment surface and/or the preform projections) or fusing.While affixing, care should be taken in order that the free overhangs orrims, and the actual heights of the preform projections are sufficientlypreserved. For example, in some embodiments, an exaggerated sinking orcompression of the projections into the attachment surface should beavoided. The proper solidity of the preform projections and thesubstrate, suitable for separating and removing both from the carriercan be decided by the skilled person, depending on the particularcircumstances.

In some embodiments, the solidity of the preform projections when theyare removed from the carrier will usually, but not necessarily, be amore solid state than when they are initially contacted with theattachment of the substrate. In some embodiments, the preformprojections should be solid enough to keep, at least partly, their shapeduring the separation from the carrier. It usually primarily meanskeeping a suitable overall shape, with particular respect to the edgeangle formed, but preserving a suitably strong bond with the attachmentsurface is also an important factor. The substrate itself shouldgenerally be solid enough to keep its form and allow the separation ofthe preform projections from the release surface. The flattened topsurface of a projection as formed can be smooth but can also be somewhatroughened, e.g., sandpaper-like or grooved, as known from the art. Thetop surface structure will be determined by the contact release surface,which generally will be essentially flat, even if naturally not planarin the true geometrical sense. In some embodiments, post treatmentscould be used that would make the top surface not essentially flat, suchas a noncontact heat treatment. Also it is possible that the carrier isnot flat so that it can form projection top surfaces that correspond tothe carrier on which they were formed.

In some embodiments of transfer methods, the attachment end of thepreform projections is less likely to be affected by long contact timeswith the carrier as there is no pressure on the attached end. That opensa possibility of letting the surface energies work for a longer time,e.g., with a lengthened carrier in a production line. In other words,the beneficial mechanical effects of the surface tensions forming theflattened ends do not have to interfere, or “compete”, with mechanicaleffects originating from an already attached end. A further advantage isthat, independently of the sizes of the particles or preformprojections, similar contact angles can be obtained for all projections.In other words the projections all are in contact with the releasesurface for the same time period and under the same conditions, which isnot the case if they were already attached to a substrate and atdifferent heights, depending on the particle size, when contacting adeforming release surface as occurs in direct forming methods. In someembodiments, this gives transfer methods a high tolerance to particlesof varied sizes. Further significant cost savings, and simplification,may be achieved by making the deformation apparatus unnecessary. Linespeed and running width of the manufacturing line can probably begreater than ever before, with lower costs. A further advantage is thatnon-thermoplastic polymers, potentially having, e.g., better mechanicalfeatures, could be used.

If small numerous projections are advantageous, it may be desirable ifat least some of the separate preform projections comprise exactly onepolymer particle per preform projection. In some embodiments, at leastsome of the preform projections are provided with contact angles ofbetween 10° and 85°, preferably 30° and 80°. In some embodiments, thiswould be the range of contact angles for most of the individual preformprojections. In some embodiments, this range would be the mean contactangle for the preform projections.

In some embodiments, at least some engaging projections are providedwith a shape in which, in each side view thereof, the engagingprojection strictly tapers (preferably is strictly convex) from theflattened top or top edge to the attachment perimeter. In someembodiments, transfer methods create semi-lenticular preformprojections, like water drops sitting on a suitable surface.

In transfer methods, non-thermoplastic and thermoplastic polymerparticles can be used, with the selection being based on, e.g.,necessary strength, required surface energy, cost, etc. In someembodiments, thermoplastics may have some advantages specific totransfer methods, which may not be obvious. First, using thermoplasticparticles and softening them after their delivery will generally ensurethat any residual molecular orientation will generally be released fromthe preform projections, at least where in contact with the carrier.Second, if the particles are thermoplastic, the viscosity of theliquefied or at least semi-liquefied material forming the preformprojections can be controlled, e.g., fine-tuned (e.g. adjusted and/oroptimized) on-line by controlling the material temperature. In someembodiments, such control may be precise, easy, cheap, and reversible.The viscosity has a direct influence on the extent to which the surfaceenergies of and between the preform projections and the contact releasesurface affect the formed contact angles. By adjusting the viscosityusing appropriately selected temperatures and heating times, the edgeangle of the final engaging projections can be fine-tuned on-line. Insome embodiments, transfer methods using thermoplastic particles canresult in inexpensive, formed fasteners with the flexibility ofadjusting the form of the fastener on-line.

If drops of liquids are deposited onto a solid carrier and if thesurface energy of the carrier is somewhat higher than the surface energy(or surface tension) of the liquid, the liquid will typically perfectlywet the solid, with a contact angle of zero. With liquids, each“solid-liquid” pair has a contact angle, between zero and 180°, withwhich the liquid drop will, approximately, wet the solid. Withsemi-liquid (e.g., softened thermoplastic) particles, the process offorming a contact angle is a time-temperature phenomenon. With solidrelease surfaces of high surface energy, a liquid polymer will wetperfectly if given enough time. If this high surface energy releasesolid surface is kept hot, and a cold solid particle is placed thereon,a process is started in which the contact angle transforms over timefrom an initial obtuse angle towards the final zero contact angle. Byinterrupting this transformation process, e.g., by a suitable cooling,one can achieve any desired contact angle. Therefore high surface energysolid carriers are useful in some embodiments of the processes of thepresent disclosure. However, the higher the carrier's surface energy,the more difficult it may be to finally separate the carrier from thepreform projections. Also if the surface energy of the carrier is toohigh in relation to that of the polymer particles, there is greateropportunity for forming a preform projection that is excessively wet tothe carrier. The risk of over-wetting the carrier is reduced if thesurface energy of the carrier is no greater than 60 mJ/m² higher thanthe surface energy of the particles.

High surface energy carriers may also cause the engaging projection'sedge angles to be too sharp, creating rims that are too thin and whichmight possibly break off during later use, creating undesiredcontamination. In some embodiments, it may be better to accept largercontact or edge angles to provide enhanced security against engagingprojections forming with thin weak edges and rims. Therefore, in someembodiments, it may be useful to provide a carrier whose surface energyis lower than the surface energy of the particles. In this case, theedge angle in the product can be determined by material selection ratherthan by on-line operating parameters. Also, generally, the lower thesurface energy of the carrier, the easier it is to finally detach thepreform projections therefrom. However a certain degree of force neededfor detaching preform projections from the contact release surface canbe beneficial. Some preform projections can be weakly affixed to theattachment surface of the fixed abrasive article substrate. Namely theaffixing strength is lower than desired for its intended end useresulting in some engaging projections possibly breaking loose duringuse. This may be a difficult defect to detect. Therefore, in someembodiments, it may be desirable if the carrier's surface energy is noless than 23 mJ/m² lower than the surface energy of the particles. Witha carrier surface energy of this level, the separation force fordetaching preform projections from the contact release surface may behigh enough to remove projections weakly affixed to the attachmentsurface thereby providing an on-line fault-detection and correctionmechanism.

In some embodiments of the methods described hereinabove forthermoplastic preform projections, the affixing of the attachmentsurface with the terminal ends of at least some of the preformprojections comprises affixing by heat or fusing. Affixing by heat caninclude melting one or the other of the preform projections or theattachment surface, depending on the materials and pressure etc. In someembodiments, both the preform projections and the attachment surface areallowed to potentially melt, and are thereby fused. Fusing is affixingof the preform projections to the attachment surface by heat. In thiscase, the preform projections are made up of particles well suited forboth being shaped by the carrier surface and being affixed to theattachment surface by fusing. The particles must be liquefied enough tosuitably form the desired contact angle, but must remain solid enough,to permit keeping their edge angles during the fusing. In someembodiments, it is preferred that the thermoplastic polymer particleshave a melt flow rate (ASTM 1238) of between 1 and 90 grams per 10minutes at the conditions appropriate for the selected polymer. In someembodiments, the melt flow rate at least 5, at least 10, or even atleast 15 grams per 10 minutes.

In the subsequent step of some transfer methods, the affixing by heatcomprises maintaining the carrier at a temperature lower than thesoftening temperature of the polymer particles or preform projectionswhile contacting the attachment surface with the attachment ends of atleast some of the preform projections. In some embodiments, the backsurface the substrate (i.e., the abrasive surface) is heated bysubjecting it to a heated gas. Furthermore, the gas pressure at theabrasive surface of the heated substrate is higher than the pressure(e.g., a gas pressure) at the attachment surface of the heatedsubstrate, thereby pressing the heated substrate against the terminalends of at least some of the preform projections to enhance the affixingthereof to the attachment surface. The pressure difference may beenhanced, for example, by applying vacuum from beneath the carrier orthe attachment surface of the substrate.

Generally, in transfer methods it is not a great problem if the preformprojections are of different heights, as long as a sufficiently pliablesubstrate, capable of bending down to reach the lower preformprojections, is provided. In some embodiments, it is especiallyadvantageous if the whole substrate is thermoplastic and is actuallysoftened, thereby made soft and flexible, easily bending or evenstretching when hot. If desired, the substrate can be fully softened,where fully softening means softening of all components and/or layersthereof, e.g. in case of a composite substrate, above a softeningtemperature.

After the separation of the substrate from the carrier, some preformprojections may remain on the carrier. These are usually very tinyresidual polymer particles which may melt into, and go away with,particles dispersed later. Still by regularly providing for theirremoval from the carrier, the process can be made more uniform andsecure. Therefore, in some embodiments, the transfer method may furthercomprise cleaning the carrier before the dispersing of the multiplicityof polymer particles on to its surface. This may involve: (1) heatingthe carrier to a temperature higher than the softening temperature ofboth the polymer particles and the front surface of a cleaning web; (2)contacting the cleaning web with the heated carrier surface therebysoftening the front surface; (3) suitably pressing the softened frontsurface against the heated carrier surface thereby fusing the polymerparticle contamination residue into the front surface of the cleaningweb; (4) providing for the carrier and cleaning web, temperaturessuitable for separating the cleaning web from the carrier; and (5)separating the cleaning web from the carrier, thereby cleaning thecarrier.

This cleaning method uses the thermoplastic character of both theparticles and the cleaning web for cleaning the carrier. During thesteps above, the small amount of residual polymer contamination goesaway with, and usually disappears in the front surface of the cleaningweb and the cleaning web can be reused. In some embodiments, no separatecleaning web may be required, as the substrate used for the abrasivearticle may be used as the cleaning web. In a continuous operation, e.g.comprising rolls or conveyors, the carrier can be cleaned with everyrevolution before each dispersing of particles, thus always keeping thecumulative carrier contamination at low levels.

In some embodiments, while the preform projections are being fused tothe attachment surface, the substrate is above the carrier where it issupported by the preform projections and bridges the space between them.If the attachment surface is above its softening temperature, anymolecular orientation therein may cause problems by shrinking at leastthe bridging portions of the substrate. That can be avoided, e.g., byusing a composite substrate with a suitable layer resistant toshrinking. For example, a substrate comprising a polyester film or paperbacking and a polyethylene layer coated thereon as a front surface canpotentially withstand the shrinking that may occur in the substrate.However, if shrinkage is a problem, it is preferable if the substrate isfree of molecular orientation when fusing the preform projections orparticles. Molecularly oriented films can be pretreated by contactingthe attachment surface of the substrate with a heated release surface(which could be the carrier), thereby rendering the attachment surfaceessentially molecularly un-oriented. The tight pressing of the carrierto the softened attachment surface during the cleaning step also canpreform this pretreating step as long as the molecular orientation issuitably released.

In some embodiments, heated gas (preferably air) at an elevated pressurecan best be provided with gas nozzles ejecting heated gas. The nozzlespreferably use electric heating for heating the gas, but the heat sourcecan be any suitable alternative heat source such as gas burners etc. Insome embodiments, if the substrate is moved in front of the outputorifice of the nozzles so that its attachment surface is contacted withthe ejected hot gas, then the substrate softens. At the same time, thehot gas ejected from the nozzles creates and maintains a gas flow alongthe abrasive surface of the substrate, typically parallel to thetraveling direction of the substrate. If the nozzles are fixed and thesubstrate is moving in a machine direction, the hot gas flow will have adirection essentially both parallel and opposite to the machinedirection. The hot gas flow, e.g. hot air flow, will exert a pullingforce on the softened substrate, dragging the attachment surface of thesubstrate that will tend to stretch the softened substrate. The fasterthe gas flows, the stronger this stretching effect will be. With a lowthroughput arrangement, i.e., with low hot gas velocities, andespecially with a thick substrate, a substrate which is essentially freeof molecular orientation can be used. In case of higher throughputs andhigher gas flow rates, and especially with a thinner substrate, thismachine direction stretching of the substrate can be very significant,which can be undesirable. For example, stretching of the substrate in alengthwise, machine direction can make it difficult to control thethickness of the fastener or can result in rolls of unspecified length.Stretching can also lead to accidental breaking by thinning and tearingapart the substrate.

The effects of stretching can be counterbalanced by providing a suitablemolecular orientation in the substrate. The problem of stretching can besolved if the substrate is provided with a heat-shrink potential in themachine direction. The heat of the gas will relax the orientation in thesubstrate, i.e., will tend to shrink the substrate, which willcounteract stretching by the heated gas flow. Therefore, in a variationof the transfer methods, one or more gas nozzles adapted for ejectingheated gas are provided. The abrasive surface of the substrate iscontacted with the heated gas ejected by the one or more gas nozzleswhile the substrate moves relative to the one or more gas nozzles. Thedirection in which the substrate is moving is the machine direction andis essentially within the plane of the substrate. The substratepreferably has a heat-shrinkability in the machine direction (thelengthwise heat shrinkability) of at least 1 percent. The affixing byheat includes heating the substrate above a heat shrink temperaturethereof.

As used herein, “heat-shrinkability” in a direction shall mean, in thecontext of a material such as the substrate material, that the materialis capable of being decreased in its length in the given direction, ordimension, in response to the transmission of thermal energy into thematerial. The “heat shrinkability” of the material is a percent valueand equals 100 percent times the difference between its pre-shrinklength and post-shrink length, divided by its preshrink length, in thegiven direction. The post-shrink length in a given direction of thematerial means the length of the material in the given direction aftershrinking the material, such as at a temperature of 170° C. for 45seconds. Shrinking can be determined, for example, by immersing thematerial into hot silicon oil and letting it freely shrink. It was foundthat using temperature of 140° C. for 14 seconds relaxes essentially allthe shrink in usual polymer materials. As used herein, the “shrinkingtemperature” of a material refers to the temperature at which thematerial, exposed to an increasing temperature, starts to heat-shrink.

The advantage of this variation of the transfer methods of thedisclosure is that it helps counteract stretching effects exerted on asoftened substrate by ejected hot gas flow. With high production rates,lengthwise heat-shrinkability higher than 1 percent can provide improvedresults. Therefore, in some embodiments, it is preferable if, in thisvariation of the transfer methods, a substrate having a lengthwiseheat-shrinkability of at least 10 percent, in some embodiments, at least20 percent, at least 30 percent, at least 40 percent, or even at least50 percent is provided for the contacting and the affixing depending onthe forces created by the hot gas flow and the production rate.

The stretching effect exerted on the substrate by a lateral hot gas flowis less significant, or even close to zero (depending on the details ofthe nozzle arrangement) in the crosswise direction, i.e., in thedirection perpendicular to the direction of the traveling path of thesubstrate (in a machine it is called the cross machine direction).Therefore, if a substrate has a high heat-shrink potential, or highheat-shrinkability in the crosswise direction, the edges of thesubstrate can shrink or neck in, which results in folding or wrinklingwhen contacted with the hot gas. Generally, this is undesirable.Therefore, in some embodiments, it is preferable if theheat-shrinkability of the substrate in its in-plane directionperpendicular to the main or machine direction is either zero, or lowerthan the lengthwise heat-shrinkability. “Zero crosswiseheat-shrinkability”, as used herein, includes the case in which thesubstrate exhibits an increase in length, or stretch, rather thanshrinking, in the crosswise direction when exposed to heat. Theadvantage of this difference in heat shrinkability is that it provides adifferentiated counteraction to the differentiated dragging effects ofthe hot gas flow on the softened substrate in the two orthogonaldimensions. Generally the heat-shrinkability of the substrate in itsin-plane direction perpendicular to the main direction (the crosswisedirection) is lower than 50 percent. In some embodiments, the crosswiseheat-shrinkability is lower than 40 percent, lower than 30 percent, oreven lower than 25 percent, depending on the forces created by the hotgas flow and the production rate. On the other hand, the substrateheated by the hot gas will exhibit a crosswise thermal expansion whichmay cause wrinkles in the product. That can be counterbalanced with asuitably low, but positive level of heat-shrinkability provided in thesubstrate in the crosswise direction. Therefore, in some embodiments, itis preferable, if, in the aforementioned situation, the crosswiseheat-shrinkability of the substrate is at least 1 percent.

As discussed above, the dragging or stretching effect in the lengthdirection from the gas nozzles is counteracted by a lengthwiseheat-shrinking, which together will generally define a final length ofthe formed fastener product as related to the initial length of theprovided substrate. If the lengthwise heat-shrinkability of thesubstrate is relatively low and the gas nozzles eject a strong hot gasflow, the fastener product will be longer than the initial substratematerial from which it was produced. By increasing the heat-shrinkpotential and perhaps decreasing the gas pressure or gas flow of thenozzles, the trend of elongated fasteners can be reversed, and theformed fastener can be shorter than the substrate from which it wasmade.

The release surface used for the pre-treating, i.e., the pre-treatingrelease surface can be similar to or different from the carrier surfacediscussed above. The pre-treating release surface must be able tosuitably release the substrate at the right time. The substratepreferably is essentially prevented from any shrinking, e.g. in order tomaintain its regular dimensions, but mainly its length. This could bedone by keeping the substrate attachment surface in full contact withthe pre-treating release surface. For that purpose, the tack between thesoftened attachment surface of the substrate and the pre-treatingrelease surface (e.g., a polytetrafluoroethylene surface) can beexploited. In order to do this, residual air between the two surfacesshould preferably be removed while contacting and pressing the substrateto the pre-treating release surface. The lengthwise heat-shrinkabilityof the substrate is decreased to a suitable value while the crosswiseheat-shrinkability rate may (and preferably will) also be decreased. Thelonger the contact time and higher the temperature, the more thedecrease in the heat-shrinkability will be and vice-versa.

A practicable manufacturing arrangement using a pre-treating stepincludes using an endless release belt with a release outer belt surfacekept in a circulating motion along a belt path. For pre-treating thesubstrate, a first portion of the outer belt surface, being at a firstlocation of the belt path, is used as the pre-treating release surface.For forming the fastener from the pre-treated substrate, a secondportion of the outer belt surface, being at a second location of thebelt path suitably displaced from the first location, is used as thecarrier. The substrate is provided in the form of a continuous substratefilm kept in a motion synchronous with the belt, and is contacted withthe outer belt surface at the first and second locations.

This solution is advantageous because a single release belt is used forpre-treating the substrate and further producing the fastener from thepre-treated substrate, which can provide for a zero length-differencebetween the initial substrate and the final product. This zerolength-difference is desired to conveniently use the same belt, runningin all of its points with the same speed, for two different purposes,i.e., for pre-treating the substrate on the one hand and for depositingthe particles to form preform projections and contacting and affixingthe pre-treated substrate therewith on the other hand. The releasesurface speed at the first location is desirably the same speed as theinitial substrate speed and the release surface speed at the secondlocation is desirably the same speed of the final formed fastenerproduct. If the decreased value of lengthwise heat-shrinkability of thesubstrate provided by the pre-treating deviates from a balance value,this section of the substrate when in free contact with the belt betweenthe first and second belt locations will tend to either get shorter orlonger. That can be detected with providing a substrate film buffer withdancing roller(s) and detecting the trend of motion of the dancingroller(s). If the free section of the substrate film between the twobelt locations should shorten, then the lengthwise heat-shrinkability ofthe pre-treated substrate could be decreased and vice versa. Thelengthwise heat-shrinkability of the pre-treated substrate can bedecreased more by elevating the temperature of the substrate at thefirst location and/or lengthening the first portion of the outer beltsurface along which the belt and the substrate are in contact therebylengthening the duration of the pre-treating of the substrate, andvice-versa. This solution has an additional advantage that the outerrelease belt surface is cleaned from any potential polymer particlecontamination by contacting the softened thermoplastic front surface ofthe pre-treated substrate with the release belt with every revolution ofthe belt.

In both transfer and direct methods, during the forming of the heatedends of the preform projections (the transfer methods) or thedeformation of the projections or particles (the direct methods), somepreform projections or particles can unify with other, neighboring,preform projections or particles. “Unify” means that two neighboringpreform projections or particles fuse or merge into a single preform orengaging projection. It is possible that preform projections orparticles portions only fuse near their tops, their attached endsremaining separate. However, it also possible that the attached endsunify with the neighboring partner preform projections or particles. Insome embodiments, only a part of the preform projections or particlesunify, while the rest remain separate, this provides a variety ofengaging capabilities. In some embodiments, a fastener with some unifiedengaging projections may provide an enhanced shear strength with respectto certain loop fabrics, e.g. low loft loops.

While not intending to be bound by any theory, the cause of thisphenomenon appears to be, first, that the elongated (in top view) shapeof the new engaging projection formed by the unification may resist ahigher torque normal to its elongated dimension. Second, the edge anglesof one of the partner merged projections, farthest from the center ofthe merged engaging projection, has edge angles that appear to be mademore acute by the unification. It is speculated that, during theunification, the polymer material of two partner projections moves fromthe projections remote edges toward their new common centre, due tocohesion, which leaves a so-called receding, decreased, contact angle atthe outer edge portions, farthest from the center or the contact line ofthe two partner projections. This allows one of ordinary skill in theart further ways to modify the engaging performance relative theparticular intended engaging loop.

In some embodiments, the unifying of neighboring projections can beeasily and inexpensively achieved, and controlled by adjusting somemanufacturing operational parameters, e.g., by adjusting the dosing rateof particles, or by using particles of different size and/or meltproperties. By increasing the density of the preform projections orparticles, a point occurs where the unifying phenomenon increases. Thisis influenced by the kind, and the shape of the particles. For example,using less spherical, more irregular particles, generally results in anincrease in unification of the particles.

In another aspect, the present disclosure provides a new fixed abrasivearticle, readily achievable through the methods above, havingcorresponding advantages.

In some embodiments, it may be advantageous if the material of theattachment surface of the substrate differs from the material of atleast one engaging projections mantle surface where they are attached.In some embodiments, it may be advantageous if the material of theattachment surface of the substrate is softer than the material of themantle surface of the at least one engaging projection as determined,for example, by differing Shore hardness values.

In some embodiments, it may be advantageous for some uses if thesubstrate is elastically extensible within a plane of the substrate, andthe material of the mantle surface of the at least one engagingprojection is non-elastomeric. The substrate can comprise elastomermaterials including elastic laminates or the like. This can make anelastic product.

In some embodiments, the engaging projections may be formed directly onthe attachment surface of the substrate of fixed abrasive article. Insome embodiments, the engaging projections may be transferred to theattachment surface of the substrate of a fixed abrasive article.

In some embodiments, the fixed abrasive article may comprise a firstsubstrate having an abrasive surface and an attachment surface, and anattachment layer. The attachment layer comprises a second substratehaving a first surface and a second surface, wherein the first surfaceof the second substrate is attached to the attachment surface of thefirst substrate. The second substrate may be the same as or differentfrom the first substrate. The attachment layer further comprises anengaging projection, as described above. Generally, any method suitablefor forming the engaging projections (e.g., the direct and transfermethods discussed herein) may be used to provide engaging elements onthe second surface of the second substrate.

In some embodiments, the second substrate may be connected (e.g.,adhered, fused, bonded, laminated) to the attachment surface of thesubstrate. In some embodiments, the first surface of the secondsubstrate is attached to the attachment surface of the first substratevia an adhesive layer, optionally wherein the adhesive layer comprisesan adhesive selected from the group consisting of a pressure sensitiveadhesive, a heat-activated adhesive.

EXAMPLES

Abrasive discs were prepared as described below with reference to eachof the particular examples. These discs were then tested using thefollowing test procedure, for purposes of comparing the performance ofdifferent discs. These examples are provided only for purposes ofillustration.

Fastener Sheet Preparation

16±5 grams per square meter (gsm) polypropylene particles (200-500micrometer diameter, “POLYAXIS PD2000”, A. Schulman, Akron, Ohio, USA)were coated onto a release surface (“CHEMGLAS 100-6”, PTFE-coated glassfiber web, Lörincz kft, Hungary). The coated release surface was passedover a hot plate set at 170±10 degrees C. to melt the polypropyleneparticles into liquid droplets. The molten droplets were then cooled tocause resolidification. An extruded polypropylene film (0.1 mm (0.004inch), 91 gsm) backing was then brought into contact with the distalends of the solidified droplets. Hot air (600±10 degrees C.) wasdirected onto the back side of the backing to fuse materials at theinterface. The backing was then cooled to effect bonding of thesolidified droplets to the backing. The solidified droplets bonded tothe backing were then separated from the release surface, therebyforming a fastener sheet having engaging projections.

Examples 1 and 2 Abrasive Article Preparation

Strips of the fastener sheet were laminated to two abrasive discs havinga PSA-coated backing (12.7 cm (5 inch) diameter, “360L P800, STIKIT”obtained from 3M, St. Paul, Minn.). A rubber roller was used to applypressure to secure the fastener sheet to the PSA-backed disc. A matchingbackup pad for the test was prepared by applying standard loop material(100% polyamide Daytona Brush Nylon loop, available from Sitip SpA ofCENE (BG), Italy) on the face of a backup pad (Model #05575, 5″diameter, STIKIT backup pad, available from 3M Co., Maplewood, Minn.)using a transfer adhesive (3M Double Coated Polyester Tape, “442 KW”,available from 3M Co of Maplewood, Minn.).

3-Mode Test

A 3-mode test was used to evaluate the adhesion of the hook-backedabrasive prototypes to the loop-faced backup pad. The test uses aranking between 0 and 10 with 5 being ideal, 0 being too low and 10being too aggressive.

The test consists of 5 evaluations. The first evaluation grades theinitial grasp. This is accomplished by placing the abrasive disc on thebackup pad and lightly slapping the disc three times. Then, the discedge is raised to determine the strength of the initial attachment.

The second evaluation (First Mode) is flat sanding for about 20 seconds.The disc is evaluated for any signs of wrinkles or release of grasp ofthe hook/loop interface on the abrasive disc edges.

The third evaluation (Second Mode) is sanding at about a 15-degree anglefrom the panel surface for about 20 seconds. The disc is evaluated forany signs of wrinkles or release of grasp of the hook/loop interface onthe abrasive disc edges.

The fourth evaluation (Third Mode) is aggressive sanding at above a40-degree angle from the panel surface for about 20 seconds. The disc isevaluated for any signs of wrinkles or release of grasp of the hook/loopinterface on the abrasive disc edges.

The fifth (and last) evaluation is the final grasp. The disc is removedfrom the backup pad and the grasp of the hook with the loop evaluated.

Examples 1 and 2 were tested using the 3-mode test. The sander used wasa 12.7 cm (5 inch) non-vacuum “Dynorbital-Spirit Random Orbital Sander”model #59020, available from Dynabrade, Inc., of Clarence, N.Y. Theworkpiece was a mild steel panel coated with a production gel coatcommonly used for boat parts, commercially available from CookComposites and Polymers of Kansas City, Mo. The test results are shownin Table 1.

TABLE 1 Results of the 3-mode test. Initial Flat ~15 degree >40 degreeExample Grasp Sanding Sanding Sanding Final Grasp 1   2.5 5 4.5 4 7 PeelDisc loose in Wrinkles, Too strength some areas, psa adhesiveaggressive, Light flaps failed before hook worked Hook/Loop into loopfabric 2 4 5 5   4 6 Crisp No flaps, Wrinkles, Too sound, good psaadhesive aggressive, good adhesion failed before hook worked peelHook/Loop into loop fabric Average 3 5 4.5 4   6.5

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

1. A fixed abrasive article comprising a substrate having an abrasivesurface and an attachment surface, an abrasive layer associated with theabrasive surface of the substrate, and an engaging projection comprisinga top surface having a top surface edge, an attachment end attached tothe attachment surface of the substrate, wherein an area of attachmentbetween the attachment end and the attachment surface is bounded by anattachment perimeter; and a mantle surface extending from the topsurface edge to the attachment perimeter; wherein at least one profileof the mantle surface is substantially convex from a point of maximumwidth along the profile to the attachment perimeter.
 2. The fixedabrasive article of claim 1, wherein the substrate comprises aforaminous substrate.
 3. The fixed abrasive article of claim 1, whereinthe substrate comprises paper.
 4. The fixed abrasive article accordingto claim 1, wherein the engaging projection is directly attached to theattachment surface of the substrate.
 5. The fixed abrasive articleaccording to claim 1, wherein at least one intermediate layer isinterposed between the attachment end of the engaging projection and theattachment surface.
 6. The fixed abrasive article according to claim 1,wherein the abrasive layer comprises shaped structures comprising acured resin binder and abrasive particles, wherein the shaped structureshave interconnected pores.
 7. The fixed abrasive article according toclaim 1, wherein the abrasive layer comprises an abrasive compositelayer comprising a plurality of precisely shaped abrasive structures. 8.A fixed abrasive article comprising a first substrate having an abrasivesurface and an attachment surface, an abrasive layer associated with theabrasive surface of the substrate, and an attachment layer, wherein theattachment layer comprises a second substrate having a first surface anda second surface, wherein the first surface of the second substrate isattached to the attachment surface of the first substrate; and anengaging projection comprising a top surface having a top surface edge,an attachment end attached to the second surface of the secondsubstrate, wherein an area of attachment between the attachment end andthe second surface is bounded by an attachment perimeter; and a mantlesurface extending from the top surface edge to the attachment perimeter;wherein at least one profile of the mantle surface is substantiallyconvex from a point of maximum width along the profile to the attachmentperimeter.
 9. The fixed abrasive article of claim 8, wherein the firstsurface of the second substrate is attached to the attachment surface ofthe first substrate via an adhesive layer.
 10. The fixed abrasivearticle of claim 8, wherein at least one of the first substrate and thesecond substrate comprises a material selected from the group consistingof paper, a foraminous substrate, and combinations thereof.
 11. Thefixed abrasive article according to claim 8, wherein the abrasive layercomprises shaped structures comprising a cured resin binder and abrasiveparticles, wherein the shaped structures have interconnected pores. 12.The fixed abrasive article according to claim 8, wherein the abrasivelayer comprises an abrasive composite layer comprising a plurality ofprecisely shaped abrasive structures.
 13. The fixed abrasive articleaccording to claim 8, wherein the abrasive layer is directly attached tothe abrasive surface of the substrate.
 14. The fixed abrasive articleaccording to claim 8, wherein the abrasive layer comprises a make coat,and abrasive particles at least partially embedded in the make coat. 15.The fixed abrasive article of claim 14, further comprising a size coatover the abrasive particles.
 16. The fixed abrasive article according toclaim 8, wherein the abrasive layer comprises a primer and abrasiveparticles attached to the primer.
 17. The fixed abrasive articleaccording to claim 8, wherein the abrasive layer comprises abrasiveparticles dispersed in a binder.